stragenmitsuko
Well-Known Member
- Joined
- Jan 19, 2016
- Messages
- 326
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Not a mechanical item , and certainly not a model but I thought this is worth sharing .
A customer wanted me to clean up the basement and discard of all items .
Amongst the items was a Samsung syncmaster F2380 , wich was a pretty high end monitor a couple of years back . Well worth the effort of trying to salvage
I hooked it up and it works for a couple of minutes , then the backlight dies .
Cycling the power brings it back to life for a couple of minutes , then it dies again . Quite repeatable .
So I opened it and started examining the pcb .
Now I've done this before , so I know what to look for . and I found exactly that .
If you look at the picture , the solder where the pencil is pointing has a little
grey cirkel in it .
That is called a cold solder . Its barely visible sometimes .
This is what caused the problem . Cold joints can have a high resistance to not making contact at all . The higher the current , the worse the problem gets .
Reflow the solder , add some real lead alloy solder , and it's fixed .
Cold joints happen when pcb are wave soldered , and sometimes there are temperature issues or a part is not clean . Causing the solder to be "glued" instead of soldered . Initially it'll work fine , but these joints make a poor electrical contact and deteriorate over the years . At bit like spark erosion in miniature .
They mostly happen on larger components with a higher thermal load .
Relais , power transistors and stuff like that .
I'de say that 50% of all electrical equippement failure in electronics are bad solder related . And the use of today's lead free alloy's makes it worse then ever .
So if your dish washer , water cooker , sewing machine or whaetever will sometimes , but not alway's work : start looking for a bad solder on one of the larger components . There 's a better then average chance you'll be able to fix it
Pat
A customer wanted me to clean up the basement and discard of all items .
Amongst the items was a Samsung syncmaster F2380 , wich was a pretty high end monitor a couple of years back . Well worth the effort of trying to salvage
I hooked it up and it works for a couple of minutes , then the backlight dies .
Cycling the power brings it back to life for a couple of minutes , then it dies again . Quite repeatable .
So I opened it and started examining the pcb .
Now I've done this before , so I know what to look for . and I found exactly that .
If you look at the picture , the solder where the pencil is pointing has a little
grey cirkel in it .
That is called a cold solder . Its barely visible sometimes .
This is what caused the problem . Cold joints can have a high resistance to not making contact at all . The higher the current , the worse the problem gets .
Reflow the solder , add some real lead alloy solder , and it's fixed .
Cold joints happen when pcb are wave soldered , and sometimes there are temperature issues or a part is not clean . Causing the solder to be "glued" instead of soldered . Initially it'll work fine , but these joints make a poor electrical contact and deteriorate over the years . At bit like spark erosion in miniature .
They mostly happen on larger components with a higher thermal load .
Relais , power transistors and stuff like that .
I'de say that 50% of all electrical equippement failure in electronics are bad solder related . And the use of today's lead free alloy's makes it worse then ever .
So if your dish washer , water cooker , sewing machine or whaetever will sometimes , but not alway's work : start looking for a bad solder on one of the larger components . There 's a better then average chance you'll be able to fix it
Pat
